the MRH Forum

Nscale helix minimum radius, maximum slope Benchwork and roadbed
Reply
Active Member 94 posts Paulc Active Member 94 posts
Paulc
I am building a new nscale layout, and am considering a helix for staging, or maybe even a second level. I am wondering what many would consider the minimum radius and slope for a helix to join 2 levels perhaps 8"-12" apart. I don't mind if trains are between for a while....it will increase run time. My average train will be probably 8-15 cars in length probably double headed. I strongly suspect that my siding length will be restricted to 10 cars max, so I likely won't be pulling anything too long up it. On another note, I would happily build my helix in an oval if that would work better. The layout will likely be l shaped to utilize two walls that meet in a corner. As always, thanks in advance, Paul

... Paul
Reply 0
Prof_Klyzlr Moderator 7,955 posts
Prof_Klyzlr

Message Search says you've asked this before???

Dear Paul,

There was a thread around 9 months ago which quite thoroughly "cook-booked" the process for designing a helix. Am not at my main machine right now, but message search (top rh corner if the MRH page) should find it in short order for you...

EDIT : These are the 2 threads, should cover almost anything you wish to ask...

  https://forum.mrhmag.com/post/smallest-radius-helix-12191643
(Um, were you the OP on this one too? Did you end up deploying any of the info provided?)

https://forum.mrhmag.com/post/figure-8-helix-12191645

Happy Modelling,
Aim to Improve,
Prof Klyzlr
Reply 0
nbeveridge Active Member 91 posts
nbeveridge

Helix Radius

For HO scale, nothing less than 30" works easily for short cars and locos, and if using full length passenger cars or modern freight cars, then 36" is the least that works easily.  I say easily because a tighter radius will work, but you must be extremely careful with the track and you may need to specially modify the cars and locos for additional coupler and truck swing and clearance.

So, since N is about half of HO, I would say use 15" or 18", according to  your rolling stock described above.

More is better.

Norman
Reply 0
Peter Pfotenhauer Regular poster 362 posts
Peter Pfotenhauer

You can go down to 15 inch

You can go down to 15 inch radii if needed, but the helix will be less of a challenge to operate if you can stay around 18 inches or more. I had no trouble getting a 2.5 inch climb at 2% in about 3/4 of a complete circle on my n scale design. If the grade is manageable you will appreciate the extra vertical clearance for the inevitable 0-5-0 rerail job that pops up unexpectedly.

A common complaint from many people is that the run time in a helix IS a significant issue for operating a train on a layout. Throttle creep comes into play, as operators get impatient to be sure the train is actually moving and sometimes subconsciously increase the throttle setting until the train comes out at unrealistic speed. Just something to consider.

 

 
Reply 0
WaltP Regular poster 134 posts
WaltP

To condense the other

To condense the other thread:

You need to decide 2 of the 3 values: Rise, Grade, Radius. They are all quite related. You then calculate the third:

Rise = Grade * 2 * PI * Radius

Grade = Radius / (Rise * 2 * PI)

Radius = (Rise / Grade) / (2 * PI)

Therefore, if you use 18" radius and a 2% Grade:  Rise = 0.02 * 2 * PI * 18 = 2.26 inches

If 2.26 inches is not enough, increase your values.

 

Put these equations in a spreadsheet to play with the values:

1A: "Helix"

2A: "Rise"

3A: "Grade"

4A: "Radius"

2C: =IF(ISNUMBER(B3);IF(ISNUMBER(B4);(B3/100)*(2*PI()*B4);"--");"--")

3C: =IF(ISNUMBER(B2);IF(ISNUMBER(B4);(B2/(B4*2*PI()))*100;"--");"--")

4C: =IF(ISNUMBER(B2);IF(ISNUMBER(B3);B2/(B3/100)/(2*PI());"--");"--")

5C: =IF(C4="--";IF(B4="--";"@@";B4*2*PI());C4*2*PI())

5D: "Run" (or "Length")

Enter values in 2B,3B, and 4B. 5C/D are just for info and displays the circumference of the circle defined by the radius.
Reply 0
Reply